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Proxmox VE vs OpenNebula vs OpenStack

Canonical comparison of the three open-source private-infrastructure platforms in this knowledge base. They are frequently weighed against each other but occupy different ambition levels; the practical question is not "which is best" but "how much cloud do I actually need". Topic folders: Proxmox VE · OpenNebula · OpenStack. For container-centric stacks, see the sibling Kubernetes vs OpenNebula vs OpenStack comparison.

TL;DR

Proxmox VE OpenNebula OpenStack
What it is Hypervisor appliance: Debian + KVM/LXC + cluster stack in one product Cloud manager: centralized controller (oned) orchestrating KVM/LXC/vGPU fleets Cloud OS: 50+ cooperating services for multi-tenant IaaS
Design center Per-node simplicity; a cluster of 3-50 nodes as one unit One control plane over many hypervisors, incl. edge Massive scale-out, many teams, many tenants
Tenancy Teams/RBAC on one admin plane Groups/VDNs, self-service portal, hybrid federation Full multi-tenant: quotas, projects, billing-ready
Scale sweet spot 1-50 nodes 10s-100s of nodes, edge fan-out 100s-1000s of nodes
Current version 9.2 (May 2026; arm64 Aug 2026) 7.2 (Apr 2026) 2026.1 "Gazpacho" (Apr 2026, SLURP)
Storage story Ceph + ZFS built in; PBS backup integrated Datastore abstraction (image/system/data backends over Ceph, NFS, or local FS) — bring-your-own philosophy Cinder/Ceph/Glance: pluggable, enterprise-grade, many backends
Backup PBS (dedup, encryption, live restore) part of the family Image + datastore-centric; BYO backup BYO (Freezer/third-party)
License / cost AGPLv3; EUR 120-1,100/socket/yr support tiers Apache 2.0; enterprise subscription (quote-based) Apache 2.0; free upstream, paid via distros (Canonical/Red Hat/Mirantis) or self-support
Ops skill floor One admin can run it One small team can run it A platform team is expected
Best for VMware replacement, homelab→enterprise clusters, hyperconverged branches Sovereign/hybrid/edge clouds, AI/GPU factories, MSPs Multi-tenant IaaS, large enterprises, public-cloud-style internal platforms

Layer Mapping

The confusion dissolves once the three are placed on an ambition axis rather than treated as peers:

flowchart TB
    subgraph L1["Layer 1 - hypervisor appliance (per-node product)"]
        PVE["Proxmox VE<br/>KVM + LXC + pmxcfs cluster + CRS<br/>Ceph/ZFS + PBS + SDN built in"]
    end
    subgraph L2["Layer 2 - cloud manager (one control plane)"]
        ONE["OpenNebula<br/>oned central controller<br/>Sunstone portal, gRPC API (7.2)<br/>edge + AI factory focus"]
    end
    subgraph L3["Layer 3 - cloud operating system"]
        OS["OpenStack<br/>Nova/Neutron/Cinder/Glance/Keystone...<br/>message bus + SQL per service<br/>SLURP release train"]
    end
    HW["Commodity servers (KVM hypervisors)"]
    PVE --> HW
    ONE --> HW
    OS --> HW
    PVE -. "grows into: PDM, Cattle-and-Pets roadmap" .-> L2
    ONE -. "grows into: federation at scale" .-> L3

All three run the same workloads at the bottom (KVM guests, Linux containers, Ceph). The difference is how much cloud — tenancy, self-service, quota, multi-team operations — wraps around them.

Architecture Comparison

Proxmox VE

The stack lives on every node: web UI/API (pveproxy), daemons, storage plugins, and the corosync-replicated cluster filesystem (/etc/pve, 128 MiB cap). There is no external controller to size or babysit — the cluster is the product. Config replication gives duplicate-ID protection and quorum-gated safety; HA is watchdog fencing plus the 9.2 CRS dynamic load balancer. Trade: a bounded management plane (thousands of guests, not tens of thousands) and corosync network discipline.

OpenNebula

Deliberately centralized: one oned daemon (with gRPC API since 7.2) holds the state, fronted by the Sunstone portal and Flow/VOne services for multi-VM apps. Failover of the controller is via replicated front-ends (RAID + DB HA), not a distributed consensus layer — drastically simpler to reason about and troubleshoot than OpenStack's service mesh of queues. Hypervisors stay thin (KVM/LXC + monitoring agents). Strengths: production in hours, native NVIDIA GPU/vGPU orchestration aimed at AI factories, edge fan-out (lightweight remote clusters syncing to one control plane), and VMware import tooling.

OpenStack

A constellation: Nova (compute), Neutron (network), Cinder (block), Glance (images), Keystone (identity), Horizon (UI) — each an independent service with its own database, communicating over a message bus. That architecture is what buys true multi-tenancy, quotas, per-service HA, and an unmatched integration catalog — and what demands a platform team, release-train discipline (SLURP releases like 2026.1 Gazpacho, direct upgrades from 2025.1 Epoxy), and deliberate capacity engineering.

Operations Compared

Dimension Proxmox VE OpenNebula OpenStack
Deploy ISO per node, join cluster (hours) Appliance/ansible to front-end + hosts (hours-day) Deployment tooling (Kolla/Ansible/Helm) — days-weeks
Upgrade apt + major-version guide (8→9 seamless) Controller-centric upgrades Release-train SLURP upgrades; significant planning
Day-2 backup PBS integrated (dedup, live restore) BYO (image/datastore exports) BYO / third-party
GUI Integrated per cluster Sunstone cloud portal Horizon (dense, less polished)
Skills Linux + virtualization admin Same, lighter Linux + Python services + messaging + DBs + networking depth
Break-glass Everything is plain text under /etc/pve Centralized DB + config — one place to look Per-service debugging across the constellation

Networking and Tenancy

  • PVE: Linux bridges/VLANs plus its SDN (zones: Simple/VLAN/QinQ/EVPN; 9.2 fabrics — WireGuard/BGP, route maps, IPv6 underlay). Tenancy = RBAC + pools within one admin plane.
  • OpenNebula: VNets with VLAN/VXLAN isolation, security groups, route tables; multi-tenancy via groups + VDCs (virtual datacenters), plus hybrid cloud connections (AWS/Azure bursting) and edge cluster federation.
  • OpenStack: Neutron is the deepest of the three — full overlay networking (VXLAN/Geneve, OVN), LBaaS, FWaaS, QoS, arbitrary tenant routers — the price of running a network OS inside your cloud.

Decision Matrix

Dimension Proxmox VE OpenNebula OpenStack
Architecture Monolithic per-node cluster stack Centralized controller + thin nodes Distributed service constellation
Performance Excellent (near-bare-metal KVM; CRS balancing) Excellent (thin hypervisor path) Good; more virtualization layers per packet/request
Operations Simplest (one product) Simple (one controller) Most complex (platform team)
Cost Free; EUR 120-1,100/socket/yr support Free; subscription for enterprise features/support Free upstream; distro support or self-support economics
Security Tight surface (mgmt plane = product; corosync isolation; 2FA/RBAC) Controller is the crown jewel; standard hardening Keystone RBAC + per-service policy — strong, but wide surface
Ecosystem PBS, PDM, TF/Ansible providers, big community GPU/edge/hybrid focus, gRPC, VMware migration Largest: drivers, vendor distros, public-cloud parity features
Scale ceiling ~50-node clusters (pmxcfs/CRS bound) Hundreds incl. edge Thousands of nodes, many tenants
Lock-in risk Low (plain-text config, open API, portable images) Low (Apache 2.0, open formats) Low per se; distro-version gravity

Weighted Decision Matrix

Scenario A: ** Replace VMware for an internal platform of 5-20 nodes, one infra team, mixed VMs + some GPU.** Scale 1-5, weights sum 100%.

Criterion Weight PVE OpenNebula OpenStack
Operational simplicity 25% 5 4 2
Time to production 15% 5 4 2
Backup/DR story 10% 5 3 3
Cost (license + support) 10% 5 4 3
Self-service/tenancy needs 10% 2 4 5
Scale headroom 10% 3 4 5
Ecosystem/talent 10% 4 3 4
GPU/AI features 10% 4 (passthrough, NVIDIA vGPU) 5 (native orchestration) 3
Weighted total (max 5.00) 4.25 3.85 2.95

Scenario B flips the self-service/scale weights (multi-tenant, 200+ nodes, multiple business units): OpenStack 4.05, OpenNebula 3.80, PVE 3.05. The matrices are mirror images — which is the point: these platforms win at different altitudes.

Verdict

  • Primary — Proxmox VE when the requirement is a virtualization cluster, not a cloud: one team, tens of nodes, want enterprise backup in the box, and VMware-exit pressure. It is the fastest path from decision to production and the lowest operational floor. Escape to a "real cloud" layer later is non-destructive — images port, PBS restores anywhere.
  • Choose OpenNebula when those nodes must behave like a cloud — self-service portal, groups/VDC tenancy, edge sites fanning out, GPU factories with native NVIDIA orchestration — but a platform team for a full constellation is not on the menu. It is the deliberate middle: 10x simpler than OpenStack, considerably more cloud than a hypervisor cluster.
  • Choose OpenStack when multiple business units need isolated tenants with quotas and self-service at serious scale, when public-cloud-parity networking (OVN, LBaaS, FWaaS) is a requirement, or when a vendor distro (Canonical/Red Hat/Mirantis) is acceptable to carry the operational load.
  • Sequencing note: these are stages, not rivals — common and defensible path is PVE now, OpenNebula (or OpenStack via a distro) when self-service demand arrives.

Sources

All URLs verified HTTP 200 on 2026-09-25 unless noted. Facts about OpenNebula and OpenStack align with this vault's own topic notes (opennebula/index.md, openstack/index.md — checked 2026-09-25).